Electrical service providers such as electrical utilities employ electricity meters to monitor energy consumption by customers (or other entities). Electricity meters track the amount of energy consumed by a load (e.g. the customer), typically measured in kilowatt-hours (“kwh”), at each customer's facility. The service provider uses the consumption information primarily for billing, but also for resource allocation planning and other purposes.
Electrical power is transmitted and delivered to load in many forms. For example, electrical power may be delivered as polyphase wye-connected or delta-connected power or as single phase power. Such various forms are known as service types. Different standard electricity meter types, known as meter forms, are used to measure the power consumption for the various service types. The commonly used meter forms in the United States include those designated as 2S, 3S, 5S, 45S, 6S, 36S, 9S, 16S, 12S and 25S meter forms, which are well known in the art.
Electrical service providers have historically billed for electrical service in arrears, using information stored within the electricity meter to determine the amount of each invoice. In a typical operation, the electricity meter stores a value representative of the amount of energy consumed in a mechanical or electronic accumulation register. From time to time, the electrical service provider obtains the value of the register and bills the customer accordingly. For example, a meter reader employed by the service provider may, each month, physically read the register value off of a meter display. The service provider then employs the obtained register value to determine the amount of electricity consumed over the month and bills the customer for the determined amount.
While electricity meters often employ electromechanical means, such as rotating disks and mechanical counters, to detect and register electricity consumption, newer meters increasingly employ digital processing circuitry instead of the rotating disk and mechanical counters. In such meters, sensors within the meter detect the voltage and current that is delivered to the load. Circuitry within the meter converts the sensed voltage and current into digital values. Processing circuitry then employs digital signal processing to calculate the quantity of consumed energy, among other things, from the digital values. Electronic meters provide greater flexibility in the types of energy consumption information that they can calculate, track, and store. Electronic meters can also facilitate remote meter reading by including a communication means such as radio communication circuits.
One of the few drawbacks of electronic meters is that the metrology and processing circuits require an electronic power supply. The power supply provides the DC bias voltage necessary for operation of digital circuits. To this end, the power supply typically operates to convert the AC line voltage into one or more usable DC voltages. In many cases, the power supply circuitry includes a voltage converter as well as voltage regulators.
While electrical power for the power supply is readily available from the AC power lines, issues can arise in the event of an electrical service interruption. During an electrical service interruption, the electronic power supply cannot operate and is unable to bias the internal circuits. As a consequence, stored data can be lost. To avoid such losses, it is known to employ temporary power from a battery or large capacitor to store critical meter data to non-volatile memory within the meter in the event of an external power interruption. The capacitor or battery provides temporary power, thereby allowing the meter to gracefully power down when the external utility power is lost.
A drawback of the prior art method of preserving data during a power outage is the requirement for a sufficient source of back-up bias power for the circuit operations that must occur to accomplish all of the power down operations. In some cases, the meter may already require a battery or capacitor to facilitate other operations, such as clock maintenance or the like. In such cases, the additional power need to operate the power down sequence can introduce additional burden. There is a need therefore, for a metering arrangement that employs power down operations with reduced component count and/or size.